Apparatus and methods for controlling transmit power of a wireless communication system

ABSTRACT

Apparatus and methods for power control in mobile communication devices are provided. In one aspect, a wireless communication device includes a transmit chain that receives a digital in-phase (I) signal and a digital quadrature-phase (Q) signal and that generates a transmit signal. The wireless communication device further includes a power amplifier that amplifies the transmit signal, and a transmit chain controller including a reference generator that combines the digital I signal and the digital Q signal and generates a reference signal corresponding to an instantaneous value of an envelope of the combined signal. The transmit chain controller further includes an error extractor that generates an error signal based on the reference signal and an output power of the power amplifier, and a control signal generator that uses the error signal to generate one or more power control signals for controlling an adjustable power level of the transmit chain.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/511,423, filed Oct. 10, 2014, and titled “APPARATUS AND METHODS FORPOWER CONTROL IN MOBILE COMMUNICATION DEVICES,” which is a divisional ofU.S. application Ser. No. 13/310,434, filed Dec. 2, 2011, and titled“SYSTEMS AND METHODS FOR POWER CONTROL IN A MULTIPLE STANDARD MOBILETRANSMITTER,” which claims the benefit of priority under 35 U.S.C.§119(e) of U.S. Provisional Patent Application No. 61/419,549, filed onDec. 3, 2010, and titled “SYSTEMS AND METHODS FOR POWER CONTROL IN AMULTIPLE STANDARD MOBILE TRANSMITTER,” the disclosures of each of whichare hereby incorporated by reference in their entireties herein.

BACKGROUND

1. Field

The present disclosure generally relates to the field of radio-frequencycommunication devices, and more particularly, to systems and methods forcontrolling power in a multiple standard mobile transmitter.

2. Description of the Related Art

As the designs of portable radio-frequency (RF) communication devices,such as cellular telephones, personal digital assistants (PDAs), WiFitransceivers, and other mobile communication devices evolve, it isdesirable to have such devices be capable of adjusting transmitted poweraccurately over a relatively wide dynamic range. For example, in theemerging markets of 3G/3.9G, linear systems such as those thatcommunicate in accordance with standards such as WCDMA, WiMAX,EUTRAN-LTE, and other non-constant envelope modulation methodologies,the requirements for those standards for accurate transmitted powercontrol continue to present challenges.

In mobile communication systems, power control can be mandated to ensurethat the respective power levels of communication signals arriving at abase station from various mobile devices are relatively the same. Toaccomplish this goal, the base station can continuously monitor thereceived signal power from each mobile device communicating with thebase station. The base station can then direct each mobile device toadjust the transmit power level depending upon one or more factors, suchas its distance, data rate change, and/or channel condition.

The presence of time-varying signal information (e.g., modulation) onthe envelope of the transmitted signal can create a conflict in designrequirements for setting the transmitted signal power and accuratelycontrolling the same during a signal transmission or burst in WCDMA andLTE communication systems. The first conflict can arise from arequirement to maintain average power step accuracy (in some cases thepower step accuracy must be maintained to within as little as ⅛ dB). Tomeet this requirement, the control loop should be relatively fast to notadversely affect the average output power level. However, if the controlloop is too fast, the control loop can strip information from the signalenvelope, introducing an error in the transmitted signal. To minimizethe impact of such errors, especially for high peak-to-average ratiomodulation formats, the bandwidth of the control loop can be kept low.It is possible to apply or switch between a control loop having abandwidth that enables a fast response and a bandwidth that permits arelatively slower response, but it takes time to ensure that the averageachieved target power when operating in the fast response mode isaccurate so that a switch to the slow response mode would not occur whenthe instantaneous error in the transmit power is substantial. Such aswitch can result in a significant error in the transmitted power for anundesirable time period.

Still another problem can arise when the modulation format or datapattern changes. While the average signal power over an entiretransmission or burst may not change, the average power during some partof the transmission could be off by more than the required power settingtolerance. If such a condition occurs when the control loop is operatingin a fast response mode (e.g., with a wide bandwidth), the control loopcould set the output power to an incorrect target value.

Conventional transmitter architectures generally apply analog powercontrol schemes by adjusting and combining elements in a transmitterchain in an effort to generate a continuous and controllable transmittedoutput power. Such transmitter chains, to be successful, use severalcontinuously variable gain elements. The performance of the elements aswell as the accuracy of the transition between them can be establishedby design, calibration information, compensation elements, andinformation regarding the supply voltage, temperature, etc. Such adesign can be extremely challenging and can require significantcalibration effort to adjust for production tolerances and temperaturevariation over a relatively wide range of operational temperatures foreach of the independent and overlapping gain/attenuation stages.

SUMMARY

Embodiments of power control systems and methods for accuratelycontrolling transmitted power in a multiple standard mobile transmittercancel a transmit signal modulation envelope within a transmit signalpower control loop. Accordingly, the mobile transmitter controlstransmitted power independent of the data pattern and absent degradationof the error vector magnitude without affecting the accuracy of thedesired transmit power.

In a number of implementations, the present disclosure relates to amobile transmitter having a transmit signal power control system thatincludes an envelope extractor, an error extractor, and a feedforwardmultiplier. The envelope extractor is configured to receive in-phase andquadrature-phase digital signal inputs and calculate an instantaneousvalue of the envelope of a combined data signal (including the in-phaseand quadrature-phase digital signal inputs), which is applied at anenvelope extractor output. The error extractor is coupled to theenvelope extractor output and to a digital representation of the outputpower generated by a power amplifier as modified by a feedbackmultiplier. The error extractor is configured to generate an errorsignal at an extractor output. The feed-forward multiplier is coupled tothe extractor output. The feed-forward multiplier configured to generatea modified error signal at a feed-forward multiplier output. In someembodiments, the modified error signal can be applied at the controlinput of a variable gain amplifier in the mobile transmitter tocontrollably adjust the power of a transmit signal. In some embodiments,the modified error signal can be used to generate coarse and finedigital control words that are coupled to a multiple stage transmitchain of analog components to controllably adjust the power of atransmit signal.

In embodiments that use a linear power detector (e.g., transmitterscommunicating using WCDMA/LTE communication protocols) a power or unitconverter can be introduced in a control signal generator, which can belocated in a feed-forward path of the control loop. In alternativeembodiments that use a log power detector (e.g., transmitterscommunicating using EDGE/GMSK communication protocols) the power or unitconverter can be introduced in the reference path of the control loop.

In some embodiments, additional transmit signal power control can beprovided by a transmit chain having a first stage, a second stage, and athird stage. The transmit chain can be configured to receive a basebandin-phase data signal and a baseband quadrature-phase data signal andgenerate a transmit signal that is coupled to a signal input of avariable gain amplifier. A transmit chain controller, coupled to thetransmit chain, can controllably adjust the gain within one or more ofthe first stage, the second stage and the third stage of the transmitchain.

In accordance with a number of implementations, the present disclosurerelates to a method for accurately controlling an adjustable power levelin a transmitter that is transmitting a data signal with a time-varyingsignal envelope. The method includes determining, in an envelopeextractor, an instantaneous representation of the data signal envelope.The method further includes generating a scaled representation of thepower at an output of a power amplifier. The method further includesgenerating an error signal as a function of both an instantaneousrepresentation of the data signal envelope and the scaled representationof the power at the output of the power amplifier. The method furtherincludes modifying the error signal as a function of the gain in afeedback path to generate a modified error signal.

In embodiments that use a log power detector to monitor the output powerof the power amplifier (e.g., transmitters communicating using EDGE/GMSKcommunication protocols), the method can further include a step ofapplying a linear to logarithmic converter to generate a scaled versionof the reference signal. In embodiments that use a linear power detectorto monitor the output power of the power amplifier (e.g., transmitterscommunicating using WCDMA/LTE communication protocols), the method canfurther include a step of applying a linear to logarithmic converter tothe modified error signal to generate a power control signal suitablefor controlling a variable gain amplifier in a transmitter.

According to some implementations, the present disclosure relates to amethod for accurately controlling an adjustable power level of a datasignal in an analog transmit chain of a transmitter. The method includesadjusting a controllable gain level of a digital-to-analog converterbased on a desired peak-to-average ratio of the transmit signalenvelope. The method further includes adjusting a digitally controlleddiscrete gain-step amplifier. The amount of gain per step is responsiveto an initial estimate of the transmitter gain and a target power at theoutput of the variable gain amplifier. The method further includesapplying a factor to a gain adjuster responsive to the gain step changein the analog transmit chain.

In some implementations, the present disclosure relates to a signalpower control system that includes a reference generator implemented toreceive and combine an in-phase digital signal and a quadrature-phasedigital signal so as to yield a combined signal. The reference generatoris further implemented to generate an output signal representative of aninstantaneous value of an envelope of the combined signal. The systemfurther includes an error extractor implemented to receive a first inputsignal including the output signal of the envelope extractor and asecond input signal including a digital representation of an output of apower amplifier. The error extractor is further implemented to generatean error signal based on the first and second input signals. The systemfurther includes a control signal generator implemented to receive theerror signal and generate one or more control signals for controlling again of an analog section of a transmit chain that provides a modulatedanalog signal to the power amplifier so as to substantially cancel amodulation envelope associated with the modulated analog signal.

In some embodiments, the power control system can include a transmitsignal power control system. In some embodiments, the referencegenerator can include an envelope extractor configured to receive andcombine the in-phase and quadrature-phase digital signals and generatethe instantaneous value of the envelope of the combined signal.

In some embodiments, the control signal generator can include an errorestimator and a logic element configured to quantify the magnitude ofthe error signal and generate a coarse power control signal and anadjustment signal. The control signal generator can further include amultiplier configured to receive as inputs the error signal and a sum ofthe adjustment signal from the logic element and an inverse of afeedback-path gain factor, the control signal generator furtherconfigured to generate a fine power control signal that reducesundesired changes in loop gain of a power control loop. The fine powercontrol signal can include a product of the inputs.

In some embodiments, the control signal generator can further include adigital adder configured to receive and add the adjustment signal fromthe logic element and the inverse of a feedback-path gain factor, thedigital adder further configured to provide the sum to the multiplier.In some embodiments, the control signal generator can further include alow-pass filter configured to remove or filter the fine power controlsignal.

In some embodiments, the transmit signal power control system can beconfigured to operate under a plurality of communication modes, such asbut not limited to WCDMA/LTE communication modes and EDGE/GMSKcommunication modes. For the EDGE/GMSK example, the reference generatorcan include a unit converter configured to receive the instantaneousvalue of the envelope and generate a converted value representative ofthe instantaneous value. The unit converter can be further configured toforward to the converted value to the error extractor. The unitconverter can include, for example, a log converter configured toperform a linear-to-logarithmic conversion.

In some embodiments, the control signal generator can include a unitconverter configured to receive at least one of the one or more controlsignals and generate a converted value. The at least one control signalcan include a fine power control signal. Such a unit converter caninclude a log converter configured to perform a linear-to-logarithmicconversion.

In accordance with a number of implementations, the present disclosurerelates to a transmitter module for a wireless device. The moduleincludes a packaging substrate. The module further includes asemiconductor die mounted on the packaging substrate. The semiconductordie includes an integrated circuit configured to provide power controlfor transmitted signal. The integrated circuit includes a referencegenerator implemented to receive and combine an in-phase digital signaland a quadrature-phase digital signal so as to yield a combined signal.The reference generator is further implemented to generate an outputsignal representative of an instantaneous value of an envelope of thecombined signal. The integrated circuit further includes an errorextractor implemented to receive a first input signal including theoutput signal of the envelope extractor and a second input signalincluding a digital representation of an output of a power amplifier.The error extractor is further implemented to generate an error signalbased on the first and second input signals. The integrated circuitfurther includes a control signal generator implemented to receive theerror signal and generate one or more control signals for controlling again of an analog section of a transmit chain that provides a modulatedanalog signal to the power amplifier so as to substantially cancel amodulation envelope associated with the modulated analog signal. In someembodiments, the transmitter module can be a part of a transceivermodule.

In some implementations, the present disclosure relates to a wirelessdevice having an antenna configured to facilitate receiving and sendingof radio-frequency (RF) signals. The wireless device further includes areceiver circuit configured to process an RF signal received from theantenna. The wireless device further includes a transmitter circuitconfigured to process an RF signal to be provided to the antenna. Thetransmitter circuit includes an integrated circuit configured to providepower control for transmitted signal. The integrated circuit includes areference generator implemented to receive and combine an in-phasedigital signal and a quadrature-phase digital signal so as to yield acombined signal. The reference generator is further implemented togenerate an output signal representative of an instantaneous value of anenvelope of the combined signal. The integrated circuit further includesan error extractor implemented to receive a first input signal includingthe output signal of the envelope extractor and a second input signalincluding a digital representation of an output of a power amplifier.The error extractor is further implemented to generate an error signalbased on the first and second input signals. The integrated circuitfurther includes a control signal generator implemented to receive theerror signal and generate one or more control signals for controlling again of an analog section of a transmit chain that provides a modulatedanalog signal to the power amplifier so as to substantially cancel amodulation envelope associated with the modulated analog signal. Thewireless device further includes a baseband subsystem configured toprovide control signals for operation of the receiver and transmittercircuits.

In some embodiments, wireless device can be configured to operate undera plurality of communication modes. Such communication modes caninclude, but are not limited to, WCDMA/LTE communication modes andEDGE/GMSK communication modes.

According to some implementations, the present disclosure relates to atransmit signal power control system for a wireless device. The systemincludes a transmit signal path having a transmit chain and one or morepower amplifiers. The transmit chain is configured to receive a digitalinput signal and generate a modulated analog signal as an input for theone or more power amplifiers. The transmit chain includes an analogsection configured to provide variable gain for the modulated analogsignal. The system further includes a control loop configured togenerate one or more control signals for adjusting the variable gain ofthe analog section of the transmit chain based on a digitalrepresentation of an output of the one or more power amplifiers and thedigital input signal, such that the transmit power control system isresponsive to a gain change but substantially non-responsive to amodulation change.

In some embodiments, the control loop can be configured so as tosubstantially cancel a modulation envelope associated with the modulatedanalog signal. In some embodiments, the substantially non-responsivenessto the modulation change can allow the transmit signal power controlsystem to operate under different communication protocols substantiallyindependent of the modulation envelope.

In a number of implementations, the present disclosure relates to amethod for controlling power of a radio-frequency (RF) signal in awireless device. The method includes generating a modulated analogsignal based on a digital input signal. The method further includesamplifying the modulated analog signal so as to yield an output signal.The method further includes generating, by a control loop, a controlsignal for adjusting a gain associated with the modulated analog signalbased on a digital representation of the output signal and the digitalinput signal. The method further includes adjusting the gain associatedwith the modulated analog signal, such that the adjusted modulatedanalog signal is substantially non-responsive to a modulation change.

In some embodiments, the adjusted modulated analog signal can beresponsive to a gain change. In some embodiments, the generating of thecontrol signal can be performed so as to substantially cancel amodulation envelope associated with the modulated analog signal. In someembodiments, the substantially non-responsiveness to the modulationchange can allow the controlling of power to be performed underdifferent communication protocols substantially independent of themodulation envelope.

Other systems, devices, circuits, methods, features, and advantages willbe or will become apparent to one with skill in the art upon examinationof the following figures and detailed description. It is intended thatall such additional systems, methods, features, and advantages beincluded within this description, be within the scope of and protectedby the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The transmitters and methods for controlling an adjustable transmitsignal power level can be better understood with reference to thefollowing figures. The components within the figures are not necessarilyto scale, emphasis instead being placed upon clearly illustrating theprinciples of how to cancel or substantially reduce the effects ofsignal modulation in a transmit signal power control loop. Moreover, inthe figures, like reference numerals designate corresponding partsthroughout the different views.

FIG. 1 is a block diagram of an embodiment of a simplified portabletransceiver including a multiple-mode transmitter.

FIG. 2 is a schematic diagram of an embodiment of the multiple-modetransmitter of FIG. 1.

FIG. 3 is a schematic diagram of an embodiment of the transmit chaincontroller of FIG. 2.

FIG. 4 is a schematic diagram of an embodiment of the transmit chain ofFIG. 2.

FIG. 5 is a flow diagram illustrating an embodiment of a method foraccurately controlling a transmit signal power level in a transmitter.

FIG. 6 is a flow diagram illustrating an embodiment of a method foraccurately controlling an adjustable power level of a transmit signal ina transmitter.

DETAILED DESCRIPTION

Although example embodiments are described in relation to a portableradio-frequency (RF) transceiver, and more specifically a transmitter ina portable RF transceiver, embodiments of the present transmit signalpower control systems and methods for controlling an adjustable powerlevel of a transmit signal can be applied in any application where acontinuous and adjustable signal power is desired.

In some implementations, power control systems and methods foraccurately controlling transmitted power in a multiple standard mobiletransmitter can include performing power control via controlled steps.Thereafter, a final target power can be achieved using a relativelynarrow range analog control loop. The analog control loop can beconfigured to cancel a transmit signal modulation envelope within thecontrol loop. Accordingly, the mobile transmitter can controltransmitted power independent of the data pattern and with absent orreduced degradation of the error vector magnitude and without affectingthe accuracy of the desired transmit power. Setting of the required RFanalog gain can be achieved via a reconfigurable local power/gaincontrol loop, which can be configured to use elements of the automatedtransmit signal power control system when the transmit power iscontrolled in an open loop mode.

The transmitters and methods for controlling an adjustable transmitsignal power level can be implemented in hardware, software, or acombination of hardware and software. When implemented in hardware, thetransmitters and methods can be implemented using specialized hardwareelements and logic. When the transmitters and methods are implementedpartially in software, the software portion can be used to controlcomponents in a transmitter or a variable gain amplifier so that variousoperating aspects can be software-controlled. The software can be storedin a non-transitory state in a memory element or elements and executedby a suitable instruction execution system (e.g., a microprocessor)coupled to the memory. The hardware implementation of the gain controlsystems and methods for controlling an adjustable transmit signal powerlevel can include any or a combination of the following technologies,which are all well known in the art: discrete electronic components, adiscrete logic circuit(s) having logic gates for implementing logicfunctions upon data signals, an application specific integrated circuithaving appropriate logic gates, a programmable gate array(s) (PGA), afield programmable gate array (FPGA), etc.

The software for the transmitters and methods for controlling anadjustable transmit signal power level comprises an ordered listing ofexecutable instructions for implementing logical functions, and can beembodied in any computer-readable medium for use by or in connectionwith an instruction execution system, apparatus, or device, such as acomputer-based system, processor-containing system, or other system thatcan retrieve the instructions from the instruction execution system,apparatus, or device and execute the instructions.

In the context of this document, a “computer-readable medium” can be anymeans that can contain, store, communicate, propagate, or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The computer-readable medium can be, forexample but not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, device,or propagation medium. More specific examples (a non-exhaustive list) ofthe computer-readable medium would include the following: an electricalconnection (electronic) having one or more wires, a portable computerdiskette (magnetic), a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), and a portable compact disc read-only memory (CDROM) (optical).Note that the computer-readable medium could even be paper or anothersuitable medium upon which the program is printed, as the program can beelectronically captured, via for instance optical scanning of the paperor other medium, then compiled, interpreted or otherwise processed in asuitable manner if necessary, and then stored in a computer memory.

In some implementations, a transmit signal path can include a number ofseries connected devices arranged in a transmit chain and one or morevariable gain power amplifiers. The transmit signal power can beadjusted by controlling signal power with the devices in the transmitchain and the one or more variable gain power amplifiers. The transmitchain can be configured to receive a digital input signal from abaseband subsystem and convert the same to a modulated analog signal,which can be applied at the input of the one or more variable gain poweramplifiers. The power at the output of the one or more variable gainpower amplifiers can be a scaled version of the power present in theinput data signal. To maintain the required averaged power step accuracyin a WCDMA/LTE transmitter, the transmitter can include a transmit chaincontroller that is configured to generate a gain control signal orsignals by comparing the power at the output of a power amplifier in thetransmit signal path with the power in the input data signal to therebygenerate or facilitate generation of an error signal. The implementationcan include a cancellation of the modulation envelope within the powercontrol loop implemented by the transmit chain controller. Accordingly,the transmitter can react to a gain change rather than the combinationof a gain change and modulation change. The error signal can be adjustedto maintain the desired gain between the input signal power and theoutput signal power of the transmit chain. Because the average amplitudeof the digital reference signal is fairly constant, the transmit signalpower at the output of the power amplifier can be well controlled.

In some implementations, a transmit chain, operating under the controlof a transmit chain controller, can be used to adjust the transmitsignal power that is applied at an input of the power amplifier. Thetransmit chain can include multiple stages of gain controllable elementscoupled in series. A first stage can include a low-power path and ahigh-power path. Each of the respective paths can include a seriescombination of an analog-to-digital converter, a low-pass filter, and amodulator. A second stage can include a step attenuator with a low-powerelement or circuit coupled to the low-power path of the first stage anda high-power element or circuit coupled to the high-power path of thefirst stage. A third stage can include a gain-step amplifier withscaling circuits coupled to the low-power element and the high-powerelement of the second stage. The output of the third stage can becoupled to the signal input of the power amplifier.

The transmit chain controller can be arranged in a closed control loopwith the transmit chain. The transmit chain controller can be configuredto receive an indication of the transmit signal power from a powerdetector, which can be coupled to one or more locations in the transmitchain. The transmit chain controller can further be configured to cancelthe modulation envelope from the transmit signal and generate coarse andfine control signals for adjusting respective elements in the transmitchain to modify the transmit signal power applied at an input to thepower amplifier.

In accordance with an illustrative or example embodiment of thetransmitters and methods for controlling an adjustable transmit signalpower level, FIG. 1 includes a block diagram illustrating a simplifiedwireless communication system 100 including a transmitter 130 with atransmit chain controller 210 and a transmit chain 300. The wirelesscommunication system 100 can include a baseband subsystem 110, aninput/output (I/O) element 112, the transmitter 130, a front-end module140, an antenna 145, and a receiver 150. The baseband subsystem 110 canbe configured to communicate with the transmitter 130 and the receiver150 via communication bus 120. The I/O element 112 can be coupled to thebaseband subsystem 110 via connection 114. The I/O element 112 canrepresent any interface with which a user may interact with the wirelesscommunication system 100. For example, the I/O element 112 may include aspeaker, a display, a keyboard, a microphone, a trackball, a thumbwheel,or any other user-interface element. A power source (not shown), whichmay be a direct-current (DC) battery or other power source, can also beconnected to the baseband subsystem 110 to provide power to the wirelesscommunication system 100. In some embodiments, the wirelesscommunication system 100 can include, for example but not limited to, aportable-telecommunication device such as a mobile cellular-typetelephone.

The baseband subsystem 110 can include microprocessor (g) 115 and memory116. The microprocessor 115 and the memory 116 can be in communicationwith each other. Depending on the manner in which the transmit chain 300and transmit chain controller 210 and methods for controlling anadjustable transmit signal power level are implemented, the basebandsubsystem 110 may also include one or more of an application-specificintegrated circuit (ASIC), a field programmable gate array (FPGA), orany other implementation-specific or general processor, among otherdevices.

The baseband subsystem 110, via microprocessor 115 and the memory 116,can be configured to provide the signal timing, processing, input,output, and/or storage functions for the wireless communication system100. In addition, the baseband subsystem 110 can be configured togenerate various control signals, such as power control signals, filtercontrol signals, and modulator control signals that are used to directvarious functions within the transmitter 130, the front-end module 140,and the receiver 150 as known to those skilled in the art. The variouscontrol signals may originate from the microprocessor 115 or from anyother processor within the baseband subsystem 110, and can be suppliedto a variety of connections within the transmitter 130, the front-endmodule 140, and the receiver 150. It should be noted that, forsimplicity, only the basic components of the wireless communicationsystem 100 are illustrated herein. It should be further noted that thetransmit chain 300 and the transmit chain controller 210 can includedigital circuits that may include additional volatile and/ornon-volatile storage elements for storing detected power levels andother parameters.

If some or all of the transmit chain 300, the transmit chain controller210 and the methods for controlling an adjustable transmit signal powerlevel are implemented in software that is executed by the microprocessor115, the memory 116 can also include power control software 118. Thepower control software 118 can include one or more executable codesegments and/or data values that can be stored in the memory 116 andexecuted in the microprocessor 115. Alternatively, the functionality ofthe power control software 118 can be coded into an ASIC (not shown) orcan be executed by an FPGA (not shown), or another device. Thefunctionality of the power control software 118 can also be provided bya suitably configured controller or processor in the transmitter 130.Because the memory 116 can be rewritable and because a FPGA isreprogrammable, updates to the power control software 118 including gainstages or ranges, calibration data, etc. can be remotely sent to andsaved in the wireless communication system 100 when implemented usingeither of these methodologies.

In one embodiment, the power control software 118 can include one ormore executable code segments for configuring the transmit chain 300 andthe transmit chain controller 210 to operate in conjunction with othertransmitter elements and the baseband subsystem 110. Once configuredand/or initialized, transmit signal power can be controlled by thecontrollable elements in the transmit chain 300. Example controllableelements can include one or more RF power amplifiers, digitalmultipliers, low-pass filters, analog-to-digital converters, modulators,step-attenuators, gain-step amplifiers, and a logic element, among otherelements that can affect the power of a RF signal. The arrangement andoperation of the transmitter elements will be explained in associationwith the functional block diagrams of FIGS. 2-6.

The transmitter 130 can include a modulator (not shown) configured tomodulate the analog signals and provide a modulated signal to anupconverter (not shown). The upconverter can be configured to transformthe modulated signal on to an appropriate transmit frequency and providethe upconverted signal to a power amplifier (not shown). The poweramplifier can be configured to amplify the upconverted signal to anappropriate power level for the communication protocol or standard inwhich the wireless communication system 100 is designed to operate. Thetransmit chain 300 and the transmit chain controller 210 can beconfigured to dynamically and selectively manage the transmitted signalpower from the wireless communication system 100 in conjunction with oneor more variable gain amplifiers.

The modulated, upconverted, amplified and power controlled transmitsignal can be forwarded to the front-end module 140 via connection 132.Details of the transmitter 130 have been omitted, as they will beunderstood by those skilled in the art. The front-end module 140 caninclude an antenna system interface that may include, for example, adiplexer having a filter pair that allows simultaneous passage of bothtransmit signals and receive signals in respective frequency ranges, asknown to those skilled in the art. The transmit signal can be suppliedfrom the front-end module 140 to the antenna 145 for signal transmissionto suitably configured communication devices, such as a base station,remote from wireless communication system 100.

In some implementations, a signal received by an antenna 145, from thebase station or other emitter, can be directed from the front-end module140 to the receiver 150 via connection 142. The receiver 150 can includevarious components to downconvert (e.g., translate in frequency),digitize, and filter a recovered data signal from a receive signal, asknown to those skilled in the art. A mixing stage can be configured todownconvert and separate the received RF signal into in-phase (I) andquadrature-phase (Q) receive signals. The I and Q receive signals can besampled and transformed into digital signals by one or moreanalog-to-digital converters (ADCs). One or more specialized digitalfilters can be introduced to further process the I and Q receivesignals.

In some embodiments, the transmitter 130 and the receiver 150 may becollocated in an integrated transceiver, such as when the transmitter130 and the receiver 150 are implemented on a radio-frequency (RF)integrated circuit (IC). In alternative embodiments, the receiver 150and the transmitter 130 can be implemented on separate ICs. Under botharchitectures, the transmit chain 300 and the transmit chain controller210 can preferably be implemented in hardware on an integrated circuitin the transmitter 130.

In some embodiments, one or more integrated circuits associated with thetransmitter 130, receiver 150, and/or transceiver can be implemented inone or more semiconductor dies. In some embodiments, one or more of suchsemiconductor dies can be implemented as a packaged module. In someembodiments, such a packaged module can include a packaging substratesuch as a laminate substrate configured to receive and connect to a dieby wirebond or flip-chip connections. The packaged module can furtherinclude packaging structures that provide functionalities such asprotection of the die and easier handling.

FIG. 2 is a schematic diagram of an embodiment of the transmitter 130 ofFIG. 1 that can support alternative wireless communication modes. Thetransmitter 130 can support both examples of WCDMA/LTE and EDGE/GMSKcommunication modes. The transmitter 130 can include a power detector200, a transmit chain controller 210 and the transmit chain 300. In someimplementations, a signal coupler 262 can provide a signal that is afunction of the signal power at the output of a power amplifier 260 tothe detector 200 on connection 253. The detector 200, which may be, forexample, a linear RF voltage detector or a RF envelope detector, can beconfigured to provide a signal on connection 205 that is a function ofthe signal on connection 253.

In some implementations, the transmit chain controller 210 can include apower monitor 220, a reference generator 230, an error extractor 240 anda control signal generator 250. The power monitor 220 can be configuredto receive the signal on connection 205 and an input on connection 203and generate a gain adjusted representation of the signal power onconnection 225. The input on connection 203 can include a factor orvariable indicative of the gain (or loss) in the feedback path. Thefeedback path can include the signal coupler 262, the detector 200, andthe power monitor 220. The power monitor 220 can be configured toconvert the received signal into a digital signal before filtering andapplying the factor to the filtered signal to adjust for signal powergain or loss in the feedback path. The gain adjusted representation ofthe signal power on connection 225 can be forwarded to the errorextractor 240.

The reference generator 230 can be configured to receive in-phase andquadrature-phase digital input signals from the baseband subsystem 110.The in-phase digital signal input can be received on connection 201. Thequadrature-phase digital input signal can be received on connection 202.The in-phase and quadrature-phase digital signal inputs can be thecomponent parts of the transmit signal, which is applied to the transmitchain 300 where it can be combined, converted, modulated and amplifiedbefore being forwarded on connection 132 to the front-end module 140(FIG. 1). The reference generator 230 can be further configured tocombine the in-phase and quadrature-phase signals and computes theinstantaneous value of the envelope of the combined signal (indicated asa reference signal), which is forwarded on connection 235 to the errorextractor 240.

The error extractor 240 can be configured to compare the gain adjustedrepresentation of the signal power that was received from the powermonitor 220 with the reference signal on connection 235 to generate anerror signal. The error signal can be forwarded on connection 245 to thecontrol signal generator 250.

The control signal generator 250 can be configured to receive the errorsignal on connection 245 and an input on connection 204 and generate oneor more control signals, which can be forwarded on connection 255 andconnection 257 to various adjustable elements in the transmit chain 300to modify the transmit signal power applied to the power amplifier 260.The input on connection 204 can include a factor or variable indicativeof the inverse of the gain (or loss) in the feedback path.

In addition to applying the inverse of the gain in the feedback path tocompensate the control loop, the control signal generator 250 can befurther configured to perform a unit conversion to compensate for thepower gains introduced in the transmit chain 300. When the transmitter130 is operating in WCDMA/LTE communication modes, the control signalgenerator 250 can apply a unit converter 252 to the generated controlsignals. The unit converter 252 can be a linear-to-logarithmic converterconfigured to compensate or adjust the one or more control signals onconnection 255 for the logarithmic gain provided in the transmit chain300 of the transmitter 130.

In some implementations, the transmit chain controller 210 can also beconfigured to support EDGE/GMSK communication modes. It can be importantto maintain closed loop control of the output power in EDGE/GMSKcommunication modes during burst transmissions because changes in poweramplifier temperature during the burst transmissions can result inundesired output power changes during the course of the burst. Thedetector 200 used to detect signal power when communicating in WCDMA/LTEmodes (e.g., a linear detector) can be replaced by a log detector. Theoutput of the log detector can be applied to the power monitor 220. Theinternal arrangement of the power monitor 220 need not change. However,as illustrated in FIG. 2, the unit converter 252 can be removed from thecontrol signal generator 250 and be inserted in the reference generator230 as a unit converter 232. In this way, the amplitude modulated signalon connection 225 from the power monitor 220 and an amplitude modulatedsignal within the reference generator 230 can both be log convertedsignals. Consequently, the error extractor 240 can be presented withsimilarly scaled input signals.

As illustrated and described, operation of the transmit chain controller210 can result in a control loop absent analysis of the data pattern,delays or inaccuracies caused by limited time averaging as wouldotherwise be applied or present in a control system that did not cancelthe data modulation. Thus, the transmit chain controller 210 can beapplied and can greatly simplify and improve transmit power controlperformance during a modulation format switch. The transmit chaincontroller 210 can further benefit an implementation of the transmitchain 300 as a combination of continuously variable and switched gaindevices.

Even though the corner frequencies of optional low-pass filters in thetransmit chain controller 210 (not shown) can be arranged to accommodatethe baseband transmit signal sampling rate and any time delay in thetransmit chain 300 (i.e., the transmit signal path) is expected to berelatively short in time, a one-time alignment of the reference pathdelay could be required to ensure that the instantaneous value of theenvelope is aligned with the transmit signal at the power amplifier 260.The one-time alignment could be implemented via delay lines or othermechanisms applied to the in-phase and quadrature-phase data inputsbefore entry into the transmit chain 300. The alignment delay could bedetermined from simulated data or in accordance with actual resultsduring a calibration of the transmitter 130.

FIG. 3 includes an example embodiment of a transmit chain controller310. The transmit chain controller 310 can be configured to receive ananalog signal from the detector 200 on connection 205 and convert thesame to a digital signal in the analog-to-digital converter 320. Theoutput of the analog-to-digital converter 320 can be coupled to alowpass filter 324 by connection 321. The low-pass filter 324 can removeor reduce signal components in the digitized representation of thesignal power above a corner frequency of the low-pass filter 324. Thelow-pass filtered signal can be forwarded on connection 325 to a digitalmultiplier 326. The digital multiplier 326 can adjust the magnitude ofthe digital representation of the signal power by a feedback-path gaincontrol factor, G_(TX), provided on connection 203, and provide a scaledversion of the signal power on connection 327 to the error extractor240.

The transmit chain controller 310 can also receive the in-phase inputsignal and the quadrature-phase input signal at the input of theenvelope extractor 332. The envelope extractor 332 can compute aninstantaneous value of the signal envelope by computing the square rootof the sum of the squares of the in-phase input signal and thequadrature-phase input signal. When the transmit chain controller 310 isoperating in WCDMA/LTE communication modes, the computed envelope valuecan be forwarded to the error extractor 240 on connection 235.Otherwise, when the transmit chain controller 310 is operating inEDGE/GMSK communication modes, the computed envelope value can beforwarded to the unit converter 232 on connection 333. The output of theunit converter 232 (e.g., a log converter) can be forwarded to the errorextractor 240 on connection 235. The error extractor 240 can calculatethe difference of the envelope at its data signal input (e.g.,connection 235 or connection 333) and the scaled version of the signalpower on connection 327 and forward the result (e.g., an error signal)to the error estimator 342 and the multiplier 360 on connection 245. Theerror estimator 342 can quantify the magnitude of the error signal onconnection 245 and forward the same on connection 343 to the logicelement 344. The logic element 344 can generate a coarse transmit powercontrol signal on connection 255 and an adjustment signal on connection345. A digital adder 350 can receive the inverse of the feedback-pathgain control factor (i.e., 1/G_(TX)) on connection 204 and theadjustment signal on connection 345 and forward the sum of theadjustment signal and the inverse of the feedback-path gain controlfactor on connection 351 to the multiplier 360. The multiplier 360 canforward the product of the error signal on connection 245 and the sum ofthe adjustment signal and the inverse of the feedback-path gain controlfactor on connection 351 to the low-pass filter 370. The multiplicationof the error signal on connection 245 with the inverse of thefeedback-path gain control factor (1/G_(TX)) can keep the loop gainsubstantially constant. The adjustment signal on connection 345 canprovide a small additive offset, which may be positive, zero, ornegative, to the inverse of the feedback-path gain control factor(1/G_(TX)), thereby providing a way to adjust the loop bandwidth, basedon the state of logic element 344. The low-pass filter 370 can remove orreduce signal components in the signal on connection 361 above a cornerfrequency of the low-pass filter 370. When the transmitter 130 isoperating in an EDGE/GMSK communication mode, a fine power controlsignal can be forwarded on connection 257 from the low-pass filter 370.Otherwise, when the transmitter 130 is operating in a WCDMA/LTEcommunication mode, the output of the low-pass filter 370 can beforwarded to unit converter 252, which can provide a linear to logconversion on the signal from the low-pass filter 370 before forwardingthe converted fine power control signal on connection 257.

FIG. 4 is a schematic diagram of an example embodiment of the transmitchain 300 of FIG. 2. As indicated above, the transmit chain 300 canreceive the in-phase (I) and quadrature-phase (Q) components of thetransmit signal from the baseband subsystem 110 and in accordance withvarious control inputs received from the transmit chain controller 210,provide an analog and scaled representation of the transmit signal onconnection 132. In some embodiments, the transmit chain 300 canaccomplish this transformation of the transmit signal via multiplestages.

A first stage 410 can include a low-power path 412 and a high-power path416. The low-power path 412 can include a series combination of adigital-to-analog converter (DAC) 413, a low-pass filter 414 and alow-power portion of a modulator 419. The high-power path 416 caninclude a series combination of a digital-to-analog converter (DAC) 417,a low-pass filter 418 and a high-power portion of the modulator 419. Thefirst stage 410 can operate in accordance with one or more controlsignals provided from the transmit chain controller on connection 257.In some embodiments, the digital-to-analog converter (DAC) 417 in thehigh-power path 416 of the first stage 410 can provide for up to 3 dB ofgain control to the power present in the transmit signal at the input ofthe transmit chain 300. In some embodiments, the digital-to-analogconverter (DAC) 413 in the low-power path 412 of the first stage 410 canprovide for up to 6 dB of gain control to the power present in thetransmit signal at the input of the transmit chain 300. In someembodiments, each of the low-pass filter 414 and the low-pass filter 418can provide a switchable 3 dB of gain to the analog signals provided atthe output of the digital-to-analog converter (DAC) 413 and at theoutput of the digital-to-analog converter (DAC) 417, respectively. Insome embodiments, controlled selection of one of the low-power portionor the high-power portion of the modulator 419 can provide a switchable6 dB of gain to the transmit signal. Alternative digital-to-analogconverters (DACs) can be used to provide control ranges other than the 3dB of gain control in the high-power path and the 6 dB of gain controlin the low-power path as may be desired.

A second stage of the transmit chain 300 can include a step attenuator420. The step attenuator 420 can include a low-power element 422 and ahigh-power element 424. The low-power element 422 can receive the outputfrom the low-power portion of the modulator 419 and forward a gainadjusted signal to a first input of the third stage. The high-powerelement 424 can receive the output of the high-power portion of themodulator 419 and forward a gain adjusted signal to a respective inputof the third stage. In some embodiments, the step attenuator 420 canhave a controlled range of about 32 dB. As indicated in FIG. 4, the stepattenuator 420 can operate in accordance with one or more controlsignals forwarded from the transmit chain controller 210 on connection255. An alternative step attenuator providing a control range of greaterthan or less than about 32 dB can be used to provide control rangesother than the 32 dB of gain control in the second stage of the transmitchain 300 as may be desired.

A third stage of the transmit chain 300 can include a gain-stepamplifier 430 having a set of scaling circuits 432. In some embodiments,the gain-step amplifier 430 can provide controlled gain from about 0 dBto a maximum gain of about 30 dB. The gain-step amplifier can alsooperate in accordance with one or more control signals forwarded fromthe transmit chain controller 210 on connection 255. The output of thegain-step amplifier 430 can be applied at the signal input of a poweramplifier 260 via the transformer 440, which performs adifferential-to-single-ended conversion, to provide a single-endedsignal to the power amplifier 260. An alternative gain-step amplifierproviding a control range of greater than or less than about 30 dB canbe used to provide control ranges other than about 0 dB to 30 dB of gaincontrol in the third stage of the transmit chain 300 as may be desired.

In some implementations, a power detector 450 can be arranged to receivesignals indicative of the power at various locations in the transmitchain 300. For example, a first power signal on connection 425 canprovide an indication of signal power at the output of the second stage420. A second power signal on connection 441 can provide an indicationof the transmit signal power on connection 132 at the signal input tothe power amplifier 260. A third power signal on connection 271 canprovide an indication of the signal power at the output of poweramplifier 260, which can be forwarded to the antenna 145 (FIG. 1). Thepower detector 450 can provide one of the first power signal, the secondpower signal or the third power signal on connection 455 to the transmitchain controller 210 in accordance with a multiplexer input (not shown).

The transmit chain controller 210 can be arranged in a closed controlloop with the transmit chain 300. The transmit chain controller 210 canbe configured to receive an indication of the transmit signal power onconnection 455 from the power detector 450 and an indication of thefeedback-path gain control factor (G_(TX)) on connection 402. Thetransmit chain controller 210 can cancel the modulation envelope fromthe transmit signal and generate coarse and fine control signals foradjusting respective elements in the transmit chain 300 to modify thetransmit signal power applied at an input to the power amplifier 260.

In operation, the example transmit signal power control as describedherein can be distributed across the multiple stages of the transmitchain 300. The transmit chain 300 and the transmit chain controller 210can operate in a closed loop for target transmitted power levels fromabout +3 dBm to maximum transmit power. Below a target transmitted powerlevel of about +3 dBm, the gain step-amplifier 430 and the transmitchain controller 210 may be disabled and the RF transmitter 130 canoperate in an open loop mode to its minimum transmitted power level.Starting with the gain-step amplifier 430 operating at or near itsmaximum output power and with the I and Q (baseband) input signals setat a nominal level, a routine could be enabled to controllably switchthe scaling circuits 432 within the gain-step amplifier 430 from thelower gain portions to the higher gain portions. In someimplementations, a preferred approach is to adjust the size of the stepchange as a function of the error identified by the error extractor 240.If the error is relatively large, the size of the step change can beincreased by N steps at a time, where N is an integer value. The stepsize could also be configured as a function of the error identified bythe error extractor 240 and a predetermined threshold. The errorextractor 240 can allow the transmit signal power level to becontrollably incremented at the gain-step amplifier 430 as long as thesignal power on connection 425 is larger than the feedback signal poweron connection 271. Additional gain changes can be implemented byadjusting the I/Q baseband signal level(s). To further lower or decreasethe transmit signal power, the step-attenuator 420 can be controllablyadjusted. In some implementations, such a step of the step-attenuatorcan be about 5 dB per step and about seven steps of control range.

In some situations, it may be desirable to implement about 4 dB in gainreduction in the local oscillator chain or the I/Q mixer switch in theI/Q modulator 419. Such control can provide possible supply currentsavings for other elements of the transmitter 130 and could reduce(e.g., improve) local oscillator leakage onto the transmit signal. Thisfiner granularity of control typically would not be utilized when arelatively large power step is required such as, for example, a stepchange of about 10 dB or greater, nor would it need to be used when thetransmitter 130 transitions from closed loop power control to an openloop mode.

The following describes operation of the system at a control transition,including how the transmit chain 300 and the transmit chain controller210 can adjust transmit signal power when control is being managed via asingle control element or one particular stage within the transmit chain300. In some implementations, the entire control system can be used fora relatively short time. In the case of an RF transmitter 130 operatingin WCDMA mode, the power control loop would typically be enabled fromabout 25 μsec prior to the WCDMA slot boundary to about 45 μsec afterthe WCDMA slot boundary. Afterwards, the I/Q baseband multiplier's valuecan be fixed as well as the gain step settings. Outside this briefwindow, elements in the control loop may be reused for other tasks.After the gain control routine is completed, the transmit signal powercontrol loop can be reconfigured to measure the gain of the nexttransition point. For example, if during the previous gain controlroutine, power was controlled based on power detection on connection425, the next routine can continue based on the signal power detected atthe input to the power amplifier 260 (e.g., the signal power onconnection 441). A self-calibration can be performed to adjust thefeedback-path gain control factor G_(TX) to nullify the error at theerror extractor 240. The new value of the G_(TX) multiplication factorcan then be stored in a memory and the previous value for G_(TX) can beapplied back as an initial condition of the transmit signal control loopfor the next time slot.

Each time the transmit signal power control system performs a gaincontrol routine it can also calibrate and store a reference level. Theoperation can remain the same regardless of whether the next step is anincrease in transmit signal power or a decrease in transmit signalpower. Between time slots, the transmit signal power control system canmonitor and store a reference value from the adjacent power monitorbranch. In some situations, the absolute reference value (e.g., thevalue stored between the time slots) is not important as it will bescaled based on the required new gain target.

The same transmit signal power control system could be reused to supportthe EDGE communication protocol as well as power ramping and powersettling to required or desired levels. In some implementations, thealgorithm of operation can be somewhat different from that describedabove. Based on the requirements of the 3G standard for maximum signalpower and the limits for spurious emissions, should the transmit signalpower raise as a step function at lower power levels, the range of thecontinuous power control can be greater than 30 dB. Continuous rampingcan be performed by adjusting the I/Q baseband signals at thedigital-to-analog converters. For the EDGE communication protocol, withthe peak to average ratio at about 3.2 dB, the nominal operating pointof the digital-to-analog converters can be about 9 dB below full scale.Prior to ramping, the nominal operating point of the I/Q basebandsignals can be reduced based on the following formula:I/Q=32−(P_(MAX)−P_(Target)), where P_(MAX) is the maximum power for therequired range of operation (e.g., 27 dBm for low bands and 26 dBm forhigh bands) and P_(Target) is the required transmit signal output powerafter the ramp. The transmit signal power control system can beconfigured to ramp up via discrete steps in an open loop mode until theantenna power approximates, for example, −4 dBm, and then the controlloop can be engaged as the system is taking the last step. At the end ofthe ramp, the I/Q multiplier can reach its final target in accordancewith the loop control and I/Q outputs can start carrying active data.During the ramp, the I/Q output can produce nearly a constant envelope.After the ramp up is complete, the loop can be maintained with minimalcapabilities. For example, limits could be placed on the range of theI/Q multiplier or the loop can be placed in a hold condition or an openloop mode. The transmit power control system can resume operation in theopposite sequence to support a transmit power ramp down.

FIG. 5 is a flow diagram illustrating an embodiment of a method 500 forcontrolling an adjustable power level. More specifically, the method 500can cancel the modulation envelope within a closed power control loop.The flow diagram of FIG. 5 shows the example architecture,functionality, and operation of an embodiment of the transmit chaincontroller 210 in generating control signals that can enable a portionof the dynamic range of the RF transmitter 130. In this regard, eachblock can represent a circuit or a module in the RF transmitter 130 thatimplements the specified function(s).

The method 500 can begin with block 502 where an envelope extractor 332can be used to determine an instantaneous representation of thetime-varying data signal envelope. As indicated above, such arepresentation can be computed by determining the square root of the sumof the squares of the in-phase and quadrature-phase input signals. Inblock 504, a power monitor 220 can be used to generate a scaledrepresentation of the power at an output of a power amplifier 260. Forexample, as shown in FIG. 3, a representation of the power at an outputof a power amplifier 260 can be generated with a power detector 200, ananalog-to-digital converter 320 and a feedback multiplier 326 thatapplies a factor, G_(TX), corresponding to the gain (or loss) from theoutput of the power amplifier 260 to the output of the feedbackmultiplier 326.

In block 506, an error extractor 240 can be used to generate an errorsignal as a function of both the instantaneous representation of thetime-varying data signal envelope produced in block 502 and the scaledrepresentation of the power at the output of the power amplifiergenerated in block 504. For example, the difference between therespective results from block 502 and block 504 can be used to generatethe error signal. In block 508, a control signal generator 240 can beused to modify or adjust the error signal generated in block 506 as afunction of the factor, G_(TX), applied in the feedback path. Theadditional gain (G_(TX)) applied in the feedback path can result in acorresponding and undesired change in the loop gain of the control loop.Accordingly, the inverse (1/G_(TX)) of the gain (G_(TX)) added (and/orlost) in the feedback path, can be applied via a feed-forward multiplier360 in the control signal generator 250.

FIG. 6 is a flow diagram illustrating an embodiment of a method 600 foraccurately controlling the power level of a data signal in a transmitchain of a transmitter. More specifically, the method 600 can generatecoarse power control signals and fine power control signals that can beapplied to respective stages of a multiple stage transmit chain 300. Theflow diagram of FIG. 6 shows the example architecture, functionality,and operation of an embodiment of the transmit chain controller 210,which when used in conjunction with the multiple stage transmit chain300 can controllably adjust the signal power applied to a signal inputof a variable gain amplifier to enable a portion of the dynamic range ofthe RF transmitter 130. In this regard, each block can represent acircuit or a module that implements the specified function(s).

The method 600 can begin with block 602 where a controllable gain levelof a digital-to-analog converter 413, 417 can be adjusted based on adesired peak-to-average ratio of the transmit signal envelope. In block604, a discrete gain-step amplifier 430 can be adjusted. As furtherindicated in block 604, the gain per step can be determined from anestimate of the transmitter gain and a target transmitter power. Inblock 606, a factor can be applied to a gain adjuster to generate acontrol signal responsive to the gain step change in the transmit chain300. The functions described above in association with blocks 602-606can be performed in sequences other than that shown in the illustratedembodiment. For example, first a coarse gain adjustment can be appliedby manipulating a discrete gain-step amplifier 430 and thereafter, afine gain adjustment can be made by manipulating the gain of ananalog-to-digital converter 413, 417 in the transmit chain 300.

After the transmit chain 300 is adjusted in accordance with thefunctions described in association with blocks 602-606, a determinationcan be made in decision block 608 whether the power in the feedbacksignal is greater than a reference or desired signal power. When thepower in the feedback signal exceeds the reference or desired signalpower, the method may optionally store the factor being applied when thefeedback signal level exceeds the reference signal level as shown inblock 610. The stored factor can then be applied as an initial orstarting value when the target transmitter power changes. Thereafter,the method 600 can terminate until the target transmitter power changes.Otherwise, when the power in the feedback signal has not exceeded thereference signal power, as indicated by the flow control arrow labeled“NO,” the functions performed in blocks 604 and 606 can be repeated.

While various embodiments of the transmitters and methods forcontrolling an adjustable power level have been described, it will beapparent to those of ordinary skill in the art that many moreembodiments and implementations are possible. For example, embodimentsof the transmitters and methods for controlling an adjustable transmitsignal power level are applicable to different types of radiotransmitters and power amplifiers and are applicable to any transmitterthat transmits a non-constant envelope signal. In addition, embodimentsof the transmitters and methods for controlling an adjustable transmitsignal power level are applicable to systems where a nearly continuousoutput signal power is desired.

The present disclosure describes various features, no single one ofwhich is solely responsible for the benefits described herein. It willbe understood that various features described herein may be combined,modified, or omitted, as would be apparent to one of ordinary skillOther combinations and sub-combinations than those specificallydescribed herein will be apparent to one of ordinary skill, and areintended to form a part of this disclosure. Various methods aredescribed herein in connection with various flowchart steps and/orphases. It will be understood that in many cases, certain steps and/orphases may be combined together such that multiple steps and/or phasesshown in the flowcharts can be performed as a single step and/or phase.Also, certain steps and/or phases can be broken into additionalsub-components to be performed separately. In some instances, the orderof the steps and/or phases can be rearranged and certain steps and/orphases may be omitted entirely. Also, the methods described herein areto be understood to be open-ended, such that additional steps and/orphases to those shown and described herein can also be performed.

Some aspects of the systems and methods described herein canadvantageously be implemented using, for example, computer software,hardware, firmware, or any combination of computer software, hardware,and firmware. Computer software can comprise computer executable codestored in a computer readable medium (e.g., non-transitory computerreadable medium) that, when executed, performs the functions describedherein. In some embodiments, computer-executable code is executed by oneor more general purpose computer processors. A skilled artisan willappreciate, in light of this disclosure, that any feature or functionthat can be implemented using software to be executed on a generalpurpose computer can also be implemented using a different combinationof hardware, software, or firmware. For example, such a module can beimplemented completely in hardware using a combination of integratedcircuits. Alternatively or additionally, such a feature or function canbe implemented completely or partially using specialized computersdesigned to perform the particular functions described herein ratherthan by general purpose computers.

Multiple distributed computing devices can be substituted for any onecomputing device described herein. In such distributed embodiments, thefunctions of the one computing device are distributed (e.g., over anetwork) such that some functions are performed on each of thedistributed computing devices.

Some embodiments may be described with reference to equations,algorithms, and/or flowchart illustrations. These methods may beimplemented using computer program instructions executable on one ormore computers. These methods may also be implemented as computerprogram products either separately, or as a component of an apparatus orsystem. In this regard, each equation, algorithm, block, or step of aflowchart, and combinations thereof, may be implemented by hardware,firmware, and/or software including one or more computer programinstructions embodied in computer-readable program code logic. As willbe appreciated, any such computer program instructions may be loadedonto one or more computers, including without limitation a generalpurpose computer or special purpose computer, or other programmableprocessing apparatus to produce a machine, such that the computerprogram instructions which execute on the computer(s) or otherprogrammable processing device(s) implement the functions specified inthe equations, algorithms, and/or flowcharts. It will also be understoodthat each equation, algorithm, and/or block in flowchart illustrations,and combinations thereof, may be implemented by special purposehardware-based computer systems which perform the specified functions orsteps, or combinations of special purpose hardware and computer-readableprogram code logic means.

Furthermore, computer program instructions, such as embodied incomputer-readable program code logic, may also be stored in a computerreadable memory (e.g., a non-transitory computer readable medium) thatcan direct one or more computers or other programmable processingdevices to function in a particular manner, such that the instructionsstored in the computer-readable memory implement the function(s)specified in the block(s) of the flowchart(s). The computer programinstructions may also be loaded onto one or more computers or otherprogrammable computing devices to cause a series of operational steps tobe performed on the one or more computers or other programmablecomputing devices to produce a computer-implemented process such thatthe instructions which execute on the computer or other programmableprocessing apparatus provide steps for implementing the functionsspecified in the equation(s), algorithm(s), and/or block(s) of theflowchart(s).

What is claimed is:
 1. A wireless communication system comprising: atransmit chain that receives a digital in-phase (I) signal and a digitalquadrature-phase (Q) signal and that generates a transmit signal, thetransmit chain having an adjustable power level controlled by one ormore power control signals; a power amplifier that amplifies thetransmit signal; and a transmit chain controller including a referencegenerator that combines the digital I signal and the digital Q signaland generates a reference signal corresponding to an instantaneous valueof an envelope of the combined digital I signal and digital Q signal,the transmit chain controller further including an error extractor thatgenerates an error signal based on the reference signal and an outputpower of the power amplifier, and a control signal generator thatgenerates the one or more power control signals based on the errorsignal.
 2. The wireless communication system of claim 1 wherein thetransmit chain controller is operable to control a transmit power of thewireless communication system substantially independent of a modulationenvelope of the transmit signal.
 3. The wireless communication system ofclaim 1 wherein the transmit chain controller further includes a powermonitor that generates a gain adjusted power signal for the errorextractor based on a detected power signal and a feedback-path gaincontrol factor.
 4. The wireless communication system of claim 3 furthercomprising a signal coupler that generates a coupled signal based on anamplified signal from the power amplifier, and a power detector thatgenerates the detected power signal based on the coupled signal.
 5. Thewireless communication system of claim 1 wherein the one or more powercontrol signals includes a fine power control signal and a coarse powercontrol signal, the fine power control signal providing a finer poweradjustment of the transmit chain relative to the coarse power controlsignal.
 6. The wireless communication system of claim 5 wherein thetransmit chain controller further includes an error estimator thatgenerates an estimate signal based on the error signal, and a logicelement that generates the coarse power control signal and an adjustmentsignal based on the estimate signal.
 7. The wireless communicationsystem of claim 6 wherein the transmit chain controller further includesa multiplier that generates a multiplied signal based on the adjustmentsignal and the error signal, the fine power control signal generatedbased on the multiplied signal.
 8. The wireless communication system ofclaim 5 wherein the transmit chain includes a digital-to-analogconverter and a gain-step amplifier, the fine power control signaloperable to control a gain level of the digital-to-analog converter andthe coarse power control signal operable to control an amount of gainper step of the gain-step amplifier.
 9. The wireless communicationsystem of claim 1 further comprising a baseband subsystem that generatesthe digital I signal and the digital Q signal.
 10. A method ofcontrolling transmit power of a wireless communication system, themethod comprising: generating a transmit signal based on a digitalin-phase (I) signal and a digital quadrature-phase (Q) signal using atransmit chain; amplifying the transmit signal using a power amplifier;combining the digital I signal and the digital Q signal to generate acombined signal; generating a reference signal corresponding to aninstantaneous value of an envelope of the combined signal; generating anerror signal based on the reference signal and an output power of thepower amplifier; generating one or more power control signals based onthe error signal; and controlling an adjustable power level of thetransmit chain using the one or more power control signals.
 11. Themethod of claim 10 wherein generating the one or more power controlsignals includes generating a fine power control signal and a coarsepower control signal, the fine power control signal providing a finerpower adjustment of the transmit chain relative to the coarse powercontrol signal.
 12. The method of claim 11 further comprising generatingan estimate signal based on the error signal, and generating the coarsepower control signal and an adjustment signal based on the estimatesignal using a logic element.
 13. The method of claim 12 furthercomprising generating a multiplied signal based on the adjustment signaland the error signal, and generating the fine power control signal basedon the multiplied signal.
 14. The method of claim 10 further comprisingdetecting the output power of the power amplifier using a coupler and apower detector.
 15. The method of claim 14 further comprising generatinga gain adjusted power signal using an output of the power detector and afeedback-path gain control factor, and generating the error signal basedon the gain adjusted power signal.
 16. A transmit chain controllercomprising: a reference generator that combines a digital I signal and adigital Q signal to generate a combined signal, the reference generatorinclude an envelope extractor that generates a reference signalcorresponding to an instantaneous value of an envelope of the combinedsignal; a power monitor that generates a gain adjusted power signalbased on a power detector signal; an error extractor that generates anerror signal based on the reference signal and the gain adjusted powersignal; and a control signal generator that generates one or more powercontrol signals for a transmit chain based on the error signal.
 17. Thetransmit chain controller of claim 16 wherein the power monitorgenerates the gain adjusted power signal based on a feedback-path gaincontrol factor.
 18. The transmit chain controller of claim 16 whereinthe one or more power control signals includes a fine power controlsignal and a coarse power control signal, the fine power control signalproviding a finer power adjustment of the transmit chain relative to thecoarse power control signal.
 19. The transmit chain controller of claim18 wherein the transmit chain controller further includes an errorestimator that generates an estimate signal based on the error signal,and a logic element that generates the coarse power control signal andan adjustment signal based on the estimate signal.
 20. The transmitchain controller of claim 19 wherein the transmit chain controllerfurther includes a multiplier that generates a multiplied signal basedon the adjustment signal and the error signal, the fine power controlsignal generated based on the multiplied signal.